1. Field of the Invention
The present invention relates to a combustion control device for internal combustion engines and a combustion method for a homogeneous lean air/fuel mixture. In more detail, the present invention relates to a combustion control device for internal combustion engines that forms a homogeneous lean air/fuel mixture inside of the cylinder of an internal combustion engine, and causes this homogeneous lean air/fuel mixture to combust by spark ignition, and a combustion method for a homogeneous lean air/fuel mixture.
2. Related Art
As an effective means for optimization of gasoline engines, lean combustion establishing the air/fuel ratio of an air/fuel mixture to be leaner than a theoretical air/fuel ratio has been proposed. Since NOx in exhaust cannot be purified with a three-way catalyst by lean combustion, for a lean-burn engine, reducing the NOX amount itself discharged from the engine, i.e. improving the combustion limit air/fuel ratio (hereinafter referred to as “lean limit”), has been important.
As one of the techniques for improving the lean limit, a technique of causing a lean air/fuel mixture to combust stably as an entire cylinder by arranging in layers comparatively lean air/fuel mixtures in the vicinity of a spark plug provided in the cylinder has been proposed (for example, Patent Documents 1 and 2).    [Patent Document 1] Japanese Unexamined Patent Application, Publication No. H10-122015    [Patent Document 2] Japanese Unexamined Patent Application, Publication No. 2002-256927